Compact oil pump for internal combustion engines



1968 R. L. WEBER ETAL 3,

-COMPACT OIL PUMP FOR INTERNAL COMBUSTION ENGINES Filed Sept. 15, 1966 2 Sheets-Sheet 1 INVENTORS ROBERT L. WEBER NOEL DWIGGINS ATTORNEYS Oct. 29, 1968 V R. 1.. WEBER ETAL 3,407,741

COMPACT OIL PUMP FOR INTERNAL COMBUSTION ENGINES Filed Sept. 15, 1966 V 2 Sheets-Sheet? I NVENTORS ROBERT L.WEBER NOEL WIGGINS ATTORNEYS United States Patent Office 3,407,741 Patented Oct. 29, 1968 3,407,741 COMPACT OIL PUMP FOR INTERNAL COMBUSTION ENGINES Robert L. Weber, Lacon, and Noel D. Wiggins, Chillicothe, Ill., assignors to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed Sept. 15, 1966, Ser. No. 579,601 8 Claims. (Cl. 103-118) ABSTRACT OF THE DISCLOSURE An oil pump for a vehicle engine has an outer gear and an eccentrically mounted inner gear which engages internal teeth on the outer gear to pump lubricant from an inlet to an outlet. The outer gear also has external teeth and the pump is driven by direct engagement of the outer gear with the engine timing gear whereby the outer gear in turn drives the inner gear. The pump may be situated within the engine timing gear housing to provide a very compact and simplified arrangement.

This invention relates to internal combustion engines and more particularly to the pumps used therein for cir culating lubricating oil through various regions of the engine.

Most forms of internal combustion engines require a pumping system for continuously providing lubricating oil to various moving elements of the engine. An advantageous type of pump for this purpose is the gear rotor pump in which an internal gear is eccentrically mounted within an outer gear of greater diameter. Teeth on the inner gear engage a larger number of teeth on the outer gear and have a configuration providing a pumping action between an inlet at one side of the inner gear and an outlet at the opposite side thereof. Such pumps, the general principles of which are well known to the art, are relatively simple, efiicient and maintenance free.

Gear pumps of this type have usually been provided with a housing which is situated on the engine in the general region of the crankcase. The internal gear of the pump has been driven by various arrangements of gears, shafts or the like which are in turn operated from the engine crankshaft. In a typical highway vehicle engine, for example, the oil pump is driven through gearing connected with the engine camshaft which in turn is coupled to the crankshaft through a set of timing gears.

The conventional structure and placement of such pumps as described above does not provide for maximum compactness and simplicity. As it has been customary to drive the pump through the internal gear at least a minimum of one additional gear or the equivalent is required and in practice, as discussed above, a fairly complex drive system is often present. The use of a separate housing and the disposition of the pump away from the crankshaft both further contribute to complication of the mechanism.

The practice of locating the oil pump in the region of the engine crankcase gives rise to still a further problem. In adapting a particular engine design to different highway vehicles it is frequently necessary that the configuration of the oil pan be changed due to clearance prob lems with axles and other such mechanisms. In prior engine constructions it has often been necessary to relocate the lubrication pump in conjunction with such changes.

The several problems discussed above are met by the present invention in an extremely simple compact and economicallymanufactured lubricating oil pump structure. -In particular, the invention uses a gear rotor type of pump which is driven through the outer gear rather than the internal gear. In contrast to the inner gear, the outer gear can readily be provided with a second set of teeth thereby eliminating any need for additional gears or other drive mechanisms. The pump is advantageously situated adjacent the timing system drive gear carried on the engine crankshaft and directly engaged therewith so that no interconnecting drive mechanism of any type is required. This placement provides for enclosing the oil pump within the same housing which contains the timing gear so that no separatehousing is required. This arrangement, in addition, removes the oil pump from the region of the oil pan so that redesigns of the latter may be made without the added complication of relocating the oil pump.

This much simplified pump construction does not of feet the configuration of the.internal sets of gear teeth which provide the pumping action and thus the basic efiiciency of this type of pump for circulating lubricant in an engine is retained.

Accordingly, it is an object of this invention to simplify the design of internal combustion engines and more particularly the lubricating oil circulation system thereof.

It is another object of this invention to provide a more compact and economically manufactured oil pump for engines.

It is still another object of this invention to provide for the positioning of an oil pump away from the regions of an engine which are subject to frequent redesign.

It is a further object of the invention to provide lubricating oil pump structure for an engine which does not require a separate housing thereon.

It is still a further object of the invention to simplify the drive connections to a gear rotor type of lubricating oil pump.

The invention, together with further objects and advantages thereof, will best be understood by reference to the following specification taken together with the accompanying drawings of which:

FIGURE 1 is a front elevation view of a truck engine embodying the invention with portions of the timing gear cover broken out to expose the oil pump mechanism therein;

FIGURE 2 is an elevation section view taken along line IIII of FIGURE 1 showing internal structure of the oil pump mechanism thereof; and

FIGURE 3 is an elevation section view taken along line III-III of FIGURE 2 and further illustrating the construction of the oil pump and the placement thereof relative to the engine crankshaft.

Referring now to the drawing and more particularly to FIGURE 1 thereof the engine 11 may be of essentially conventional construction except insofar as the oil pumping mechanism 12 thereof is concerned and thus has an engine block 13 with a crankshaft 14 journalled therein. As is customary in such engines, a timing: drive train gear 16 is mounted on the crankshaft 14 at the front of the engine and enclosed by a cover 17 secured to the engine block 13. An oil pan 18 is disposed along the underside of the block.

The oil pump 12 in the present invention is situated adjacent the timing system drive gear 16 and is driven thereby so that in effect the pump is directly driven from the crankshaft without requiring any intervening drive mechanism complications. To provide further simplification the cover 17 of the timing gear 16 is extended and suitably shaped, as will hereinafter be discussed in more detail, to receive the components of the pump 12.

Pump 12 is of the type in which an inner rotatable gear 19 with external teeth 21 is disposed within an annular outer gear 22 having a greater number of matching interrial teeth 23. In this example'theinn ergear 19 has four teeth 21 and the outer gear 22 carries five teeth 23. Inner gear 19 is rotatable about an axis offset from that of the outer gear 22 providing pumping regions 24 between the teeth 21 and 23. Considerations which determine the configuration of the teeth 21 and 23, the relative pitch diameters of the gears 19 and 22, and the appropriate offset between the rotary axes of the gears to effect an optimum pumping action are well understood within the art. For ease of manufacture and to increa-se durability, the gears 19 and 22 are formed of sintered metal.

Referring now to FIGURES 2 and 3 in conjunction, the outer gear 22 is disposed within a conforming concavity 26 in the "inner face of the timing gear cover 17, and is rotatable therein. Outer gear 22 is retained in concavity 26 by a plate 27 secured against the inner face of the timing gear cover 17 by bolts 28. The inner gear 19 is journalled on an axle 29 extending from the timing gear cover 17 to plate 27, the axle being offset from the axis of the outer gear 22 as hereinbefore described.

To admit lubricating oil to the pump 12 an intake passage 31 is provided in the lower portion of plate 27 and communicates with the pumping region space 24 below inner gear 19. An oil outlet passage 32 in the upper portion of plate 27 communicates the pumping region 24 above the inner gear 19 with an oil distribution passage 33 formed within the top portion of the timing gear cover 17. The connections to the intake and outlet passages 31 and 32 of the pump 12 may be conventional and are well understood within the art.

Oil pumps of this general class utilize a relief valve 34, best shown in FIGURE 3, to relieve excess pressure in the outlet passage 32. Relief valve 34 is contained within a bore 36 in plate 27 between intake and outlet passages 31 and 32, the bore having an open end 37 to admit a slidable valve rod 38 therein. A compression spring 39 is disposed in bore 36 to urge the valve rod 38 away from the open end 37, the spring being held in position by an apertured retainer 40 and snap ring 41 at the open end 37 of the bore. Valve rod 38 has a section 42 of reduced diameter and a terminal land portion 43 of intermediate diameter at the end remote from the open end 37 of bore 36.

A passage 44 in plate 27 connects the pump outlet 32 with the region of bore 36 adjacent the reduced diameter section 42 of valve rod 38. A second passage 46 in the plate 27 connects pump intake 31 with the bore 32 at a region closer to the open end 37 thereof. Thus the valve rod 38 normally block the flow of oil between passages 44 and 46. However if the oil pressure within the pump outlet 32 increases to the point where the force of spring 39 is overcome rod 38 slides within bore 36 to a position at which rod section 42 connects the two passages 44 and 46 thereby relieving the excess oil pressure within the pump outlet. Return movement of the valve rod 38 toward the closed position of valve 34 is damped by the oil trapped behind the land portion 43 of the valve rod. As such oil can only escape slowly past the land 43, chattering of the valve rod 38 from slight pressure fluctuations and the like is prevented.

It has heretofore been the common practice to operate engine oil pumps of this general class by driving the inner gear 19 which in turn drives the outer gear 22. This inherently requires a more complicated drive connection than is utilized in the present invention. In the present invention the outer gear 22 is the driving member and for this purpose is provided with external gear teeth 47 which directly engage the timing gear 16 on crankshaft 14. Owing to this unique construction of the outer gear 22 and the placement of the pump for direct engagement of the teeth 47 with a gear 16 already present on the crankshaft 14, no external elements are needed forthe.

purpose of driving the oil pump 12. The result is an extremely compact and economically manufactured system with no sacrifice in pumping efificiency. Further, the arrangement situates the oil pump away from those regions of the engine which are. subject to frequent redesign to adapt the engine to different types of vehicle.

What is claimed is:

1. A lubricating oil pump for an engine of the class having a crankshaft comprising, in combination, an annular outer gear mounted on said engine in a rotatable manner and coupled to said crankshaft for rotation thereby, said outer gear having internal gear teeth, an inner gear of less diameter than said outer gear disposed therein for rotation about an axis offset from the rotary axis of said outer gear, said inner gear having external teeth which are less in number than said internal teeth of said outer gear and which engage said internal teeth of said outer gear whereby a pumping region is formed between said teeth of said inner and outer gears, said inner gear 'being driven through said engagement with said outer gear, and means forming an inlet passage communicating with a first portion of said pumping region and forming an oil outlet passage communicating with a second portion of said pumping region.

2. A lubricating oil pump for an engine as defined in claim 1 wherein said engine has a drive train gear mounted on said crankshaft and wherein said outer gear of said oil pump is directly engaged therewith.

3. A lubricating oil pump for an engine as defined in claim 1 wherein said engine has a timing system drive gear mounted on a forward portion of said crankshaft and wherein said outer gear of said oil pump has external teeth directly engaging said timing system gear.

4. A lubricating oil pump for an engine as defined in claim 1 wherein said engine has a timing system drive gear mounted on said crankshaft and enclosed by a timing gear cover and wherein said outer gear of said oil pump has external teeth directly engaging said timing system gear, and wherein said timing gear cover extends to cover said outer gear and form a housing for said oil pump.

5. A lubricating oil pump for an engine as defined in claim 4 wherein said outer and inner gears of said oil pump are disposed within a concavity of said timing gear cover.

6. A lubricating oil pump for an engine as defined in claim 4 wherein said outer and inner gears of said oil pump are journalled within a concavity in said timing gear cover, said concavity having a diameter similar to that of said outer gear, and wherein said means forming oil inlet and outlet passages comprises a plate secured to said timing gear cover over said concavity therein, said passages being within said plate.

7. A lubricating oil pump for an engine as defined in claim 1 wherein said inner and outer gears of 'said oil pump are formed of sintered metal.

8. A lubricating oil pump for an engine as defined in claim 1 wherein said engine has a timing system drive gear mounted on said crankshaft at the forward end of said engine and wherein said outer and inner gears of said oil pump are mounted on said engine at the forward face thereof for rotation about axes parallel to the axis of rotation of said crankshaft, said outer gear being adjacent said timing system gear and having external teeth directly engaged therewith.

References Cited UNITED STATES PATENTS HOUSTON S. BELL, JR., Primary Examiner.

Disclaimer 3,407,74l.-Robert L. Weber, Lacon and Noel D. Wiggins, Chillicothe, Ill. COM- PACT OIL PUMP FOR INTERNAL COMBUSTION ENGINES. Patent dated Oct. 29, 1968. Disclaimer filed Mar. 11, 1981, by the assignee, Caterpillar Tractor Co.

Hereby enters this disclaimer to claims 1, 2, 3 and 8 of said patent.

[Oflicial Gazette May 26. I981 

